Downdraft tubular boiler



D v OBRIEN DOWN DRAFT TUBULAR BOILER.

Patented Mar. 31,1891.

UNITED STATES PATENT OFFICE.

DENNIS V. OBRIEN, OF BOSTON, MASSACHUSETTS.

DOWNDRAFT TUBULAR BOILER.

SPECIFICATION forming part of Letters Patent No. 449,381, dated March31, 1891.

Application filed January 3, 1891. Serial No. 376,593. (No model.)

.To aZZ whom it may cancer/u:

Be it known that I, DENNIS V. OBRIEN, of Boston, in the county ofSufiolk and State of Massachusetts, have invented certain new and usefulImprovements in Downdraft Tubular Boilers, of which the following is aspecification.

This invention relates to downdraft tubular boilers; and it has for itsobject to provide a large area of heating-surface exposed to the heatedproducts of combustion from the furnace at a point where the heat is themostintense.

The invention consists in the interposition of a short tubularboiler-section between the rear end of the grate and the usualtube-sheet which supports the front ends of the boilertubes, saidsection comprising two tube-sheets located near each "other at the'rearend of the grate, and inclosing a water-space which communicates withthe usual water-spaces of the boiler and a number of tubes connectedwith said sheets below the grate, said tubes conducting the products ofcombustion through the said water-space, so that the water therein issubjected to the action of a high degree of heat, the products ofcombustion passing directly from the grate through the said sec tion,and from thence to the usual longitudinal tubes of the boiler through achamber between said section and the usual tube-sheet, all of which Iwill now proceed to describe and claim.

The accompanying drawing represents a sectional perspective View of aboiler embodying my invention.

In the drawing,- (t represents the outer shell of the boiler, and arepresents the section or portion of the inner shell, which, with thecrown-sheet c, surrounds the fire-box 7; and ash-pit 712'.

g represents the grate, and f a tube-sheet, which supports the rear endof the grate and extends across the space inclosed by the crown-sheet cand shell a, said tube-sheet extending vertically from the crown-sheetto the bottom of the shell a, and entirely across said shell. frepresents another tube-sheet of the same form and size as the sheet fSaid sheet f with the shorter crown-sheet c, shell a and tube-sheet fconstitute a combustionchamber 1', separated from thegrate by thewater-space between the tube-sheets f f The sheetsf f support a largenumber of short tubes f which are located below the grate and conductthe heated products of combustion from the space below the grate throughthe water-space between the sheets f f to the combustion-chamber t'.

It will be observed that the tube-sheets f and f and the tubes f thereinconstitute a short section of tubular boiler, the water-space of whichcommunicates on all sides with the usual water-spaces of the boiler, sothat there is a free circulation of water through said section. Thetubes f being located below the grate and constituting the only outletfor the products of combustion, cause a downward draft through the grateand afford large areas of surface on which the highly-heated products ofcombustion, fresh from the bed of burning fuel, act. The location ofsaid tubes below the grate also causes the products of combustion toenter the lower portion of the chamber 1 so that the natural tendency ofheat to rise will insure a thorough distribution of heat in saidchamber, so that each of the usual elongated tubes 21, extending fromthe tube-sheet f through the main body of the boiler, will be heated topractically the same degree as all the others, the heat being equalizedthroughout the chamber 2'.

It will be seen that the tube-sheet f and the tubes If have the sameform and arrangement as in ordinary boilers, the distinguislr ingfeature of my invention being the two additional tube-sheets ff and thetubesf connected therewith, the whole forming a shorttubularboiler-section located close to the grate and having its tubes locatedbelow the grate.

I am aware that downdraft boilers have been made in which a dependingwater-leg supports the rear end of the grate, said waterleg terminatingjust below the grate, so that the products of combustion pass through alarge opening between the lower end of the water-leg and the bottom oftheinner shell of the boiler, there being no direct connection betweenthe interior of the water-leg and the water-space at the bottom of theboiler below the ash-pit. Boilers so constructeddo not have that largearea of heating-surface exposed to thehighly-heated products ofcombustion fresh from the fire that is presented by the short tubularboiler-section of my invention. Hence the action of the water-leg boilerin generating steam is not so rapid nor so economical of fuel as that ofmy improved boiler. Moreover, the said water-leg does not constitute avertical passage or conduit communicating at its bottom or lower endwith the waterspace at the bottom of the boiler, but terminates in aclosed bottom just below the grate, said bottom affording aresting-place for sediment which, owing to the intense heat at thispoint, is very liable .to cause the burning of the metal. My improvedtubular section, on the other hand, opening into the water-space at thebottom of the boiler, affords no surface for the accumulation ofsediment or scale, there being a continuous circulation through the saidsection from bottom to top.

In addition to the advantages of my improvement above specified, anotheri m portan t advantage is the increased strength imparted to the boilerby the two fiue-sheetsff the same extending entirely across the innershells of the boiler, vertically as well as hori zontally, and beingconnected all around their edges by rivets r with the said inner shell.

I claim- The improved downdraft tubular boiler having the inclinedgrate, the tube-sheet located at a distance from the rear end of thegrate and supporting the forward ends of the ordinary tubes, the shorttubular boilersection interposed between the grate and the flue-sheet atthe rear end of the grate and composed of the tube-sheets extendingentirely across the inner shell of the boiler, vertically as Well. ashorizontally, and the short tubes in said sheets located below thegrate, said short tubular section being separated from the tube-sheet bya chamber, into the lower portion of which the products of combustionpass through the tubes of the tubular section, the tubes and tube-sheetscomposing said section presenting large areas of heating-surface to thehighly-heated products of combustion close to and below the grate, asset forth.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing Witnesses, this 17th day of December, A. D.1890.

DENNIS V. OBRIEN. iVitnesses:

O. F. BROWN, EWING W. HAMLEN.

